Comment (by Erik Schnetter):

There are some optimizations that recompile code at link time. I don’t think these were ever successfully used in Cactus, nor whether compilers offer them any more. (The current set of -lto optimizations might store the compiler flags internally.)

So far, the Cactus policy has been that each stage (preprocessor, compiler, linker) gets passed all the flags of the previous stages.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2553/cactus-link-command-used-cppflags-and